Selling a commodity for someone who asks for it before buying and possessing it

Question 50: I agreed with someone to buy a car for him. I told him that its price in the agency is 50,000 riyals and that I would take 60,000 riyals if I got it for him. Is this lawful?

Answer: There is no problem in selling the car or any other commodity after you have bought it and kept it in your possession. You can sell it for an instant payment or for a higher deferred payment, whether by installments or not. Allaah (Exalted be He) says: …whereas Allaah has permitted trading and: O you who believe! When you contract a debt for a fixed period, write it down. This includes deferred payment… read more here.